Provide interim statistics while in mid-checkpoint. Re-implements similar functionality in 9.1 and previously which was removed during split of checkpointer and bgwriter.
Provide interim statistics while in mid-checkpoint.
Re-implements similar functionality in 9.1 and previously which
was removed during split of checkpointer and bgwriter.

Requested/spotted by Magnus Hagander

kmjungersen/PostgresXL,techdragon/Postgres-XL,ashwinstar/gpdb,yazun/postgres-xl,postmind-net/postgres-xl,50wu/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,yazun/postgres-xl,jmcatamney/gpdb,lisakowen/gpdb,Postgres-XL/Postgres-XL,greenplum-db/gpdb,ashwinstar/gpdb,tpostgres-projects/tPostgres,adam8157/gpdb,lisakowen/gpdb,yazun/postgres-xl,xinzweb/gpdb,oberstet/postgres-xl,jmcatamney/gpdb,ovr/postgres-xl,tpostgres-projects/tPostgres,greenplum-db/gpdb,postmind-net/postgres-xl,zeroae/postgres-xl,xinzweb/gpdb,50wu/gpdb,zeroae/postgres-xl,kmjungersen/PostgresXL,snaga/postgres-xl,arcivanov/postgres-xl,jmcatamney/gpdb,arcivanov/postgres-xl,adam8157/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,adam8157/gpdb,arcivanov/postgres-xl,oberstet/postgres-xl,pavanvd/postgres-xl,kmjungersen/PostgresXL,zeroae/postgres-xl,Postgres-XL/Postgres-XL,xinzweb/gpdb,ovr/postgres-xl,snaga/postgres-xl,50wu/gpdb,xinzweb/gpdb,zeroae/postgres-xl,kmjungersen/PostgresXL,50wu/gpdb,adam8157/gpdb,snaga/postgres-xl,zeroae/postgres-xl,50wu/gpdb,Postgres-XL/Postgres-XL,techdragon/Postgres-XL,tpostgres-projects/tPostgres,oberstet/postgres-xl,lisakowen/gpdb,greenplum-db/gpdb,lisakowen/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,adam8157/gpdb,postmind-net/postgres-xl,arcivanov/postgres-xl,jmcatamney/gpdb,adam8157/gpdb,yazun/postgres-xl,ashwinstar/gpdb,greenplum-db/gpdb,ovr/postgres-xl,50wu/gpdb,tpostgres-projects/tPostgres,50wu/gpdb,techdragon/Postgres-XL,lisakowen/gpdb,techdragon/Postgres-XL,lisakowen/gpdb,lisakowen/gpdb,xinzweb/gpdb,ovr/postgres-xl,ovr/postgres-xl,tpostgres-projects/tPostgres,adam8157/gpdb,lisakowen/gpdb,jmcatamney/gpdb,pavanvd/postgres-xl,arcivanov/postgres-xl,50wu/gpdb,arcivanov/postgres-xl,Postgres-XL/Postgres-XL,oberstet/postgres-xl,xinzweb/gpdb,greenplum-db/gpdb,snaga/postgres-xl,yazun/postgres-xl,postmind-net/postgres-xl,pavanvd/postgres-xl,pavanvd/postgres-xl,greenplum-db/gpdb,kmjungersen/PostgresXL,postmind-net/postgres-xl,oberstet/postgres-xl,Postgres-XL/Postgres-XL,ashwinstar/gpdb,techdragon/Postgres-XL,adam8157/gpdb,xinzweb/gpdb,snaga/postgres-xl,xinzweb/gpdb,pavanvd/postgres-xl